Roof is the floor of upper house

Dear son, at your birth,
At your school admission,
At your college entrance,
At each stage of your progress,
I beamed with pride
That I built a nest to rest in
If and when I go invalid
Till I rather late realized
That the time you had your family,
That you wanted to use the nest
To bring up your progeny.
Rather than providing me a sanctuary.

Every old one collapses likewise.
Of course, you are my extension.
13.06.2001, Chennai